Subquery's in WHERE en SELECT
Data joinen in SQL
Maham Faisal Khan
Senior Content Developer, DataCamp
Syntaxis voor subquery's in WHERE
- Alle semi-joins en anti-joins die we hebben gezien, hadden een subquery in
WHERE WHEREis de meest voorkomende plek voor subquery's
Syntaxis voor query's met het WHERE IN-statement
SELECT *
FROM some_table
WHERE some_numeric_field IN (4, 8, 12);
Syntaxis voor subquery's in WHERE
SELECT *
FROM some_table
WHERE some_field IN
(include subquery here);
Syntaxis voor subquery's in WHERE
SELECT *
FROM some_table
WHERE some_field IN
(SELECT some_numeric_field
FROM another_table
WHERE field2 = some_condition);
Subquery's in SELECT
SELECT DISTINCT continent
FROM states;
|---------------|
| continent |
|---------------|
| Africa |
| Asia |
| Europe |
| North America |
| Oceania |
|---------------|
Subquery's in SELECT
SELECT DISTINCT continent,(SELECT COUNT(*) FROM monarchsWHERE states.continent = monarch.continent) AS monarch_count FROM states;
| continent | monarch_count |
|---------------|-----------------|
| Africa | 0 |
| Asia | 2 |
| Europe | 2 |
| North America | 0 |
| Oceania | 0 |
Laten we oefenen!
Data joinen in SQL
